Two different flow channel configurations on thermal resistances associated with the behavior of cooling of power device were studied in this paper. ANSYS Icepak 14.0 has been adopted as a numerical simulation tool. The simulation results from this study showed that the shapes of channels in cooling radiator play an important role in the thermal management of water cooling radiation system. The optimal channel design could improve the heatdissipating efficiency by 80% in water cooling radiation system. The result also indicated that the thermal resistance of heat sinks decreased with the volumetric flow rate and the number of cylindrical columns in the flow channel. Experimental results were obtained under certain channel configurations and volume rates. Moreover, the results of numerical simulation can be explained well by the experimental results.